(copyright) Copyright, Ray Chapman 1996. All of the material in this patent application is subject to copyright protection under the copyright laws of the United States and of other countries. As of the first effective filing date of the present application, this material is protected as unpublished material.
However, permission to copy this material is hereby granted to the extent that the owner of the copyright rights has no objection to the facsimile reproduction by anyone of the patent document or patent disclosure, as it appears in the United States Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
In general, the present invention relates to an apparatus and process for separating the constituent components of Printed Wiring Assemblies (hereinafter xe2x80x9cPWA""sxe2x80x9d) and Printed Wiring Boards (hereinafter xe2x80x9cPWB""sxe2x80x9d) (i.e., the unpopulated boards and trim scrap from which the unpopulated boards are produced). In particular, the invention relates to a dry, mechanical process and an associated apparatus whereby PWA""s or PWB""s are successively and repeatedly crushed into a granular mixture of materials, which may be separated into granular forms of non-metallic and metallic constituent components suitable for reclamation, recycling, and reuse.
Over the past three decades, since the inception of the integrated circuit and the computer, consumer acceptance combined with technological advances has produced an exceptionally strong market for electrical/electronic products that use integrated circuits and computers for the distribution and manipulation of information and data. The integrated circuits are often encapsulated in ceramic packages, mounted on PWB""s to form PWA""s, and, ultimately, packaged in various electrical or electronic equipment and appliances (i.e., plastic compartments). PWA""s have become ubiquitous in such items as personal and business computers, telecommunications equipment, television sets, and other consumer electronic systems. Normal wear-and-tear and the extraordinary rate of technological change in the capabilities PWA""s and PWB""s have combined to produce a dramatic increase in the amount of obsolete electronic equipment produced in recent years. Despite the fact that much of this unusable or unwanted equipment contains a multitude of hazardous ingredients including copper and lead, much of this equipment is disposed of by simply placing it in private or municipal landfill sites. This approach is problematic for a variety of reasons. For instance, this approach has the potential for leaking toxic materials into the environment (i.e., water table). In addition, this approach unnecessarily dedicates limited landfill capacity. Consequently, consumer, business, and governmental entities are increasingly directed at the ecologically sound disposal of such equipment and have an intensifying interest in recycling the raw materials such equipment contains.
The disposal of PWA""s and PWB""s, however, involves special problems. Some of the special problems of properly disposing and/or recycling electrical/electronic equipment and appliances relate to the manner in which PWA""s and PWB""s are manufactured. PWB""s are made by laminating two or more layers of fiberglass reinforced epoxy or polyimide resins with copper foil. The laminate is then coated with a metallic material, usually copper, upon which circuits are traced by a variety of imaging and etching techniques. In addition to quality defects that produce unusable PWB""s, the process for producing finished, etched PWB""s creates up to 20% waste as trim scrap. Because the material from which PWB""s are made is a thermoset, the base can not be remelted and reused once it is produced. Similarly, PWA""s are produced from PWB""s by soldering or otherwise affixing functional components, such as chips having integrated circuits (hereafter xe2x80x9cIC""sxe2x80x9d), connectors and other components to the base. The composition of these components includes such precious metals as Gold, Silver, Palladium and Platinum, which are encapsulated in ceramic or epoxy resins.
Some existing techniques dispose of PWA""s and PWB""s in the following fashion. PWA""s may be stripped of any reusable components. The partially depopulated PWA""s are then sent to a smelter where they are pyrolized to burn off volatile constituents and then crushed. The resulting ash is then reduced by melting and the precious and semi-precious metals are recovered through several pyrometallurgical stages. The value of the precious metals is then calculated, after subtracting the cost of the smelting process, and this value is returned to the supplier of the PWA""s.
This process has several disadvantages when complete PWA""s are sent directly to smelters:
the smelting process is inherently costly in term of energy usage;
the pryolsis process produces air pollutants that must be scrubbed from oven stacks or otherwise converted into carbon dioxide, which is an environmentally unfriendly substance;
the resulting xe2x80x9csludgexe2x80x9d from the smelting process is returned to the landfill, which uses up limited landfill capacity and, in some circumstances, may leak into the environment; and
sampling techniques to determine the precious metal content of the PWA""s prior to the smelting operation are impractical and unreliable.
Alternatives to the direct smelting of PWA""s include techniques that seek to separate various metal constituent components from the non-metallic constituent components of complete electrical/electronic systems. These techniques include mechanical crushing of electrical/electronic units followed by magnetic separation to remove ferrous metals, followed either by sink flotation techniques to remove lighter weight non-metallic or metallic constituent components; or by density separation techniques followed by treatment of the resulting metallic or non-metallic portions with strong acids, bases or toxic cyanide; or by elaborate series of grinding and density separation steps to completely separate such metals as copper from aluminum and nickel. These approaches still require hazardous components such as Cathode Ray Tubes (CRTs), mercury switches, and Polychlorobiphenly containing capacitors, frequent components of electronic assemblies, to be removed manually. In addition, they involve chemical or water treatment that requires careful and costly monitoring of effluents for hazardous ingredients and/or are costly with respect to the value of the reclaimed materials.
Generally, in preferred embodiments, PWA""s, are removed from electrical or electronic systems, either manually or by a gross shredding operation that is performed on the assembled unit after hazardous items, such as CRTs, mercury switches and Polychlorobiphenyl containing capacitors, are removed. Alternatively, PWB""s are simply provided to preferred embodiments. Then, PWB""s and/or PWA""s are successively and continuously crushed to reduce the overall size of the constituent components. The resulting constituent components contain a mixture of metallic and non-metallic base materials and are separated from one another using the specific gravity of the fractions of material produced. This mechanical process of repeated size reduction and separation generally renders PWA""s or PWB""s into three fractions: (A) a granular form of the metallic constituent that allows reproducible and reliable chemical analysis of its elemental composition and permits efficient reclamation of the precious elements through subsequent refining processes; (B) a finely ground form of non-metallic PWB base material, generally comprising fiberglass and epoxy or polyimide resin, a xe2x80x9cfinesxe2x80x9d fraction; and (C) an extremely finely ground form of non-metallic dust generally comprising the fiberglass and binding resins from the PWB base. These fractions are produced in various proportions depending on the composition of the PWA or PWB feed stock. Fractions (B) and (C) may be combined, together or separately, with other materials to produce composites that may be used in construction or industrial applications. These applications include, but are not limited to, sinks, desktops, highway lane dividers, highway sound barriers, electronic component cases, chemically resistant floor grating, tile, shingles, molding compounds, highway speed regulators, kitchen and bathroom countertops, and wallboard. Therefore, all components of PWA""s or PWB""s can be returned to constructive use rather than being placed in landfill sites. Because this process is completely dry and requires no incineration or chemical treatment steps, associated problems of monitoring effluent water, air or chemical waste streams are avoided.
Specifically, preferred embodiments of the apparatus that are used to separate metallic and non-metallic constituent components from various types of PWA""s/PWB""s comprise a plurality of crushing machines, a plurality of screens, and a plurality of separators. Each crushing machine (i.e., ring mills, radial knife granulators, roll crushers, jaw crushers, ball mills, disk granulators, impact mills, and hammer mills) has a crushing machine entry port and a crushing machine exit port. In addition, each crushing machine of the plurality of crushing machines has at least one screen of the plurality of screens affixed thereto and positioned to screen each crushing machine exit port to selectively allow passage of specifically sized products. The specifically sized products passed through a first screen are larger than the specifically sized products allowed to be passed through a second screen, wherein the first screen precedes the second screen. Preferred embodiments use two (2) crushing machines. The at least one separating machine receives products from the crushing machine exit port of at least one crushing machine of the plurality of crushing machines via a plurality of conveyors, such as a belt conveyor and a closed conveyor. The at least one separating machine (i.e., a gravity separator, such as a fluidized bed separator, electrostatic separators, electrodynamic separators, vibrating screen separators, and destoners) separates the at least one electronic products into the non-metallic constituent components, the metallic constituent components, and into a grouping of mixed constituent components. Note the metallic constituent components are generally heavier than the non-metallic constituent components; the metallic constituent components generally have a higher specific gravity than the non-metallic constituent components. The grouping of mixed constituent components is transported to one crushing machine entry port of one crushing machine of the plurality of crushing machines via a feedback mechanism, such as one as a conveyor, to form a closed loop for further size reduction and ultimate separation. Note that a plurality of conveyors can also be collectively used as a feedback mechanism. Each conveyor has a conveyor entry port and a conveyor exit port. A first conveyor of the plurality of conveyors is positioned is transport the at least one electronic component to a first crushing machine entry port of a first crushing machine of the plurality of crushing machines. The at least one second conveyor of the plurality of conveyors is positioned to receive and transport at least one first crushed electronic component crushed by the first crushing machine from the first crushing machine exit port to the second crushing machine entry port of the second crushing machine of the plurality of crushing machines.
In addition, in preferred embodiments, at least one opening of the plurality of openings of the first screen allow passage of specifically sized products having diameters between {fraction (1/16)}xe2x80x3 and 2xe2x80x3 and at least one opening of the plurality of openings of the second screen allow passage of specifically sized products having diameters between {fraction (1/16)}xe2x80x3 and 1xe2x80x3. Similarly, a least one opening of the plurality of openings of the first screen allows passage of specifically sized products having diameters between xc2xexe2x80x3 and 1xe2x80x3 and at least one opening of the plurality of openings of the second screen allows passage of specifically sized products having diameters between {fraction (3/16)}xe2x80x3 and xe2x85x9cxe2x80x3. Preferred embodiments may also comprise a plurality of air separators (i.e., a cyclone air separator, Air Classifiers, Air Stratifyers, Centrifugal Air Classifiers, Venturi Separators, Trickle Vane Separators, and Rising Current Density Separators). Each air separator has an air separator entry port and an air separator exit port. Each air separator entry port is positioned to remove light weight materials from the at least one crushed electronic product. Each air separator removes dust from the light weight materials and returns the light weight materials to one conveyor of the plurality of conveyors. Each air separator exit port is mechanically linked with a collection apparatus (i.e., a bag house filter) to filter and gather the dust. A shredder may also be used to shred the at least one electronic product to create at least one shredded electronic component. The at least one shredded electronic component is then transferred to the first crushing machine entry port of the first crushing machine. Belt conveyors can be used to transfer material to and from the shredder. The first crushing machine, the second crushing machine, and the separator may be maintained under a partial vacuum to permit collection of dust in a closed collector.
Preferred processes to separate metallic and non-metallic constituent components of at least one electronic product are generally comprised of the following steps: (a) repeatedly crushing the at least one electronic product to create a plurality of crushed electronic components; (b) repeatedly screening the plurality of crushed electronic components to ensure that the plurality of crushed electronic components substantially conform to a specific size; and (c) repeatedly separating portions of the plurality of crushed electronic components after steps (a) and (b) into non-metallic constituent components, metallic constituent components and mixed constituent components by weight, the mixed constituent components having both non-metallic constituent components and metallic constituent components; and (d) returning the mixed constituent components to be recrushed, rescreened, and reseparated in steps (a), (b), and (c). In addition, before step (a), the at least one electronic product must be provided or otherwise transported to crushing machines to perform step (a). Likewise, the crushed electronic components must be transported from one crushing machine to another crushing machine and to the separating apparatus to perform step (c). The crushed electronic products are also periodically screened, such as after each crushing step to limit the size of the crushed materials in the stream of crushed materials being evaluated. Portions of the light weight material that comprise metallic material are preferably returned to the stream of crushed material. Lightweight material is also removed from the stream of crushed materials by at least one air separator. Portions of lightweight material substantially comprised of non-metallic materials (i.e., dust) are transported to a collection apparatus. The products can be shredded before step (a).
Preferred embodiments provide a number of advantages. Preferred embodiments substantially (and in some cases completely) recycle the constituents/components of PWA""s and PWB""s by separating the metallic from the non-metallic constituent components of which they are made and return all of these raw materials to reuse rather than sending them to a landfill, thereby reducing the dedication of limited landfill space to the disposal of electrical/electronic equipment. Preferred embodiments do not require incineration or chemical or water treatment procedures, which avoids potential problems with air or water pollution, to separate metallic and non-metallic constituent components of PWA""s/PWB""s. In addition, preferred embodiments perform the separation and recovery of metallic and non-metallic constituent components in a cost efficient way and in a manner that reclaims the maximum amount of precious and semiprecious metals from these materials.
Other advantages of the invention and/or inventions described herein will be explained in greater detail below.